1. Field of the Invention
The present invention relates to a positioning system, a position information transmitter, a communication terminal, and a control method of the positioning system and, particularly, to a technology that enables stable and reliable acquisition of the current position of the communication terminal.
2. Background Art
A system utilizing radio signals transmitted from artificial satellites such as GPS satellites (hereinafter, satellite positioning signals) has a problem that the positioning accuracy deteriorates or positioning becomes impossible when a communication terminal such as a GPS receiver enters an area where the satellite positioning signals may not be received such as an indoor area, a street with buildings, or an underground mall.
Therefore, for example, Japanese Patent Application Laid-Open Publication No. 2007-278756 discloses a technology of providing an apparatus transmitting a position information signal, which is a signal indicative of a position, to an area where the satellite positioning signals may not be received such as an indoor area or an underground mall to allow the communication terminal to receive the position information signal and acquire the current position.
To enable stable and reliable acquisition of the current position of a communication terminal by a communication terminal capable of positioning with the satellite positioning signal and positioning with the position information signal as in the above technology, an arrangement is required to appropriately determine which of the satellite positioning signal or the position information signal should be received to set the operation state of the communication terminal.